Thousands of miles of buried fiber optic cable in densely populated coastal regions of the U.S. may soon be inundated by rising seas, according to a new study by researchers at the University of Wisconsin-Madison and the University of Oregon.

The study portrays critical communications infrastructure that could be submerged by rising seas in as soon as 15 years, according to the study’s senior author, Paul Barford, a UW-Madison professor of computer science.

Seawater inundation projected for New York City by 2033 and its effect on internet infrastructure. Undersea cables, long-haul fiber cables, and metro fiber cables are shown. Anything in the blue-shaded areas is estimated to be underwater in 15 years due to climate change-induced sea level rise as projected by the National Oceanic and Atmospheric Administration. Courtesy of Paul Barford/University of Wisconsin-Madison.
“Most of the damage that’s going to be done in the next 100 years will be done sooner than later,” Barford said. “That surprised us. The expectation was that we’d have 50 years to plan for it. We don’t have 50 years.”

The study, conducted with Barford’s former student Ramakrishnan Durairajan, now of the University of Oregon, and Carol Barford, who directs UW-Madison’s Center for Sustainability and the Global Environment, is the first assessment of risk of climate change to the internet. It suggests that by the year 2033, more than 4,000 miles of buried fiber optic conduit will be underwater and more than 1,100 traffic hubs will be surrounded by water. The most susceptible U.S. cities, according to the report, are New York, Miami, and Seattle, but the effects would not be confined to those areas and would ripple across the internet, potentially disrupting global communications.

The peer-reviewed study combined data from the Internet Atlas, a comprehensive global map of the internet’s physical structure and projections of sea-level incursion from the National Oceanic and Atmospheric Administration. Many of the conduits at risk are already close to sea level and only a slight rise in ocean levels due to melting polar ice and thermal expansion as climate warms will be needed to expose buried fiber optic cables to seawater. Barford said hints of problems to come could be seen in the catastrophic storm surges and flooding that accompanied hurricanes Sandy and Katrina.

Buried fiber optic cables are designed to be water-resistant, but unlike the marine cables that ferry data from continent to continent under the ocean, they are not waterproof. Risk to the physical internet is coupled to the large population centers that exist on the coasts, which also tend to be the same places where the transoceanic marine cables that underpin global communication networks come ashore. Moreover, much of the data that transits the internet tends to converge on a small number of fiber optic strands that lead to large population centers like New York, one of the more vulnerable cities identified in the study.

The impact of mitigation such as sea walls, according to the study, are difficult to predict.

“The first instinct will be to harden the infrastructure,” Barford said. “But keeping the sea at bay is hard. We can probably buy a little time, but in the long run it’s just not going to be effective.”

In addition to looking at the risk to local and long-haul infrastructure in the nation’s coastal areas, the study examined the risk to the buried assets of individual internet service providers. It found the networks of CenturyLink, Inteliquent, and AT&T to be at highest risk. The researchers say these findings serve notice to industry and government.

“This is a wake-up call,” Barford said. “We need to be thinking about how to address this issue.”